[exim] giving some sender hosts a higher priority?

Hi,

Is it possible to give some hosts a higher priority when relaying messages?

As I am relaying for several different hosts (companies) and some of them
have different expectations than others.
ie some have time sensitive emails and some arent so bothered about their
messages being delivered immediately.

The best way would be to put them on different servers, but that is not
economical at the moment.

Thanks,

Oliver